Air Pressure, Sound Testing and Air Testing Services UK

Head Office: Sayells Farm, 7 Harlington Road, Upper Sundon, Bedfordshire, LU3 3PE
Tel: 07967 233836 or 07775 623464
Email: info@airpressuretesting.net
Offices in London, Luton and Cardiff

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Thermographic Testing


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Thermographic Testing

Why Infrared Thermal Imaging Surveys

Thermographic Surveys
Air Pressure Testing have many years experience of carrying out thermographic surveys and can offer clients advice at an early stage as to the most productive method to carry out a thermographic survey.

Air Pressure Testing wide ranging technical and practical experience of building technology, design issues and potential faults in buildings allows us to give a high level of service both in carrying out the survey and interpreting the results.

Building thermography is a method of indicating the heat distribution over the surface of a building envelope. This remote-sensing technique can be carried out with minimal disturbance by one of our engineers and allows qualitative detection of air leakage pathways and insulation discontinuities. The survey will be carried out using an un-cooled thermal imaging camera, which can measure temperatures to 0.1°C and displays the images and reports in full colour. Air Pressure Testing uses a calibrated FLIR infrared camera, which allows full analysis of saved images.

Thermographic Surveys are carried out to BS EN 13187:1999: Thermal performance of buildings - qualitative detection of thermal irregularities in building envelopes - infra-red method and BRE Report 176 - A Practical Guide To Infra-Red Thermography For Building Surveys.

On-site Requirements For Thermographic Surveys
The following outlines the requirements for the above test. Areas of discontinuous insulation will be more readily identified in these conditions:

• Drawings (plans and sections) and specification details regarding the areas to be surveyed should be supplied prior to the survey taking place
• The integrity of the building envelope should be complete for the survey
• APT have assumed that the survey will be carried out from the outside of the building, usually at night (or on an overcast day in winter) when the weather is dry.
• It is important that the internal temperature of the building is 10°C higher than the external
• If possible, the internal pressure of the building should be raised by 10 Pascals by switching off the extract units

An hand-held infra-red sensitive camera records images of the subject that are compared to conventional pictures of the same areas. "Hot-spots" can then be related to features of the building and an informed view taken of building integrity. Local/component thermography whilst a building is depressurised can identify where air tightness needs improving.

Golden rules to ensure Part L is met
You must ensure there is a minimum temperature differential between inside and outside the building of at least 10°C. This is usually achieved by leaving the heating system turned on inside the building for 12 – 24 hours prior to the survey.

Carry out external Thermographic surveys after dark (or heavy cloud), to ensure problems with sunlight warming up external surfaces can be ignored. Ensure the weather is dry as moist surfaces play havoc with the survey results. Beware items of plant emitting heat inside a building, as they can affect the results.

Why use Thermographic cameras?

A thermal image makes it easy to identify areas of missing, misplaced or discontinuous insulation.
It can also be used to identify air leakage paths if used correctly. Cold air leaking into a building will cause cold patches on the surrounding fabric, which can be identified from thermal images.

Can Thermographic surveys quantify air leakage?

No, but they provide a qualitative appreciation of the thermal properties of a building envelope, quickly over large areas and display the results graphically in colour. Spot temperatures are also measured which can allow for later analysis of the thermal performance of building envelopes, again especially useful in highlighting areas of misplaced or discontinuous insulation, something Air Leakage Testing cannot
How can you interpret the thermal images?

A sound knowledge of construction technology and a sound knowledge of the projects design (U values, emissivity of materials) allied with experience of on site defects is required to identify the true cause of faults identified on site. Particular care needs to be taken with regard to the emissivity and reflectivity of surfaces. Surfaces with low emissivity (e.g. polished steel), appear colder than their surroundings but are sensitive to reflective heat from background sources e.g. equipment, lights, people etc.

When To Get Worried
If the thermal image of the inside face of a building envelope appears to have a low surface temperature compared to their surroundings. Take care to evaluate the results as this could be caused by;

• Missing or damaged insulation or maybe high levels of moisture within the building fabric
• High levels of air leakage cooling the inside face
• Thermal bridging
• Evaporation of moisture from the internal surface
• Cold rooms inside the building cooling the surroundings

 

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